Melanotic oncocytic metaplasia of the nasopharynx

We present three cases of melanotic oncocytic metaplasia of the nasopharynx. Case 1 and Case 2 were a 70- and a 61-year-old woman, and Case 3 was a 74-year-old man. Although Case 1 was asymptomatic, Cases 2 and 3 had hoarseness. All cases were Japanese and their nasopharyngeal examination revealed single or multiple black nodules measuring a few millimeters in diameter. In each case, biopsies were performed to rule out malignancy. Histological examination showed respiratory mucosa with oncocytic metaplasia and melanin pigments. Immunohistochemically, S-100 protein and melan-A positive dendritic melanocytes were observed in the basal layer of the oncocytes. Melanotic oncocytic metaplasia is extremely rare, and so far only 21 cases have been reported in the English literature to our knowledge. It has been reported in only older Asians, predominantly in males; there have been only three female patients including our two cases. All of our cases were long-time smokers, which supports the previously described hypothesis that smoking may be a predisposing factor for melanin pigmentation. Since melanotic oncocytic metaplasia may clinically mimic a malignant tumor, it is important to be aware of this lesion.